The birthright customarily involved a double portion of the inheritance (Deuteronomy 21:17), but this privilege also involved the spiritual leadership of the family. Esau desired the first but not the second. In any case, the father was responsible to transfer the birthright to a more deserving son if necessary (1 Chronicles 5:1,2), and Isaac should have long since made it clear that it was to go to Jacob. The latter, appalled at the thought of a carnal profligate like Esau having the spiritual responsibilities of the birthright, offered to purchase it from him, perhaps initially in jest. However, Esau agreed to the absurd bargain, thus making it even more clear that he was unqualified.